1. Field of the Invention
The invention relates to the delivery of molten metal for casting purposes and, more particularly, to a mobile holding furnace having a metering pump capable of dispensing contamination-free molten metal in discrete quantities.
2. Description of the Prior Art
Various techniques are known for dispensing molten metal for casting purposes in a foundry. Crane-carried ladles have been used for many years to transfer molten metal from a furnace or holding tank to individual molds. So-called metering pumps have been used to transfer molten metal in discrete quantities from a furnace or holding tank to a gating system which, in turn, conveys the metal to individual molds. U.S. Pat. No. 4,078,706 to S. Hanuszczak and U.S. Pat. No. 4,474,315 to R. E. Gilbert et al, the disclosures of which are incorporated herein by reference, disclose metering pumps suitable for dispensing molten metal from a furnace or holding tank to individual molds.
The chief drawback of the referenced molten metal transfer techniques is that molten metal is susceptible to being oxidized and/or contaminated during passage of the molten metal from the furnace or the holding tank to the molds. In part, this is because the ladles and gating systems are exposed to the atmosphere. If the highest quality castings are desired, the presence of oxidation or contaminants is unacceptable.
One possible approach to solving the problem would be to provide mobile molds which could be moved very close to the furnace or holding tank. Another possible approach would be to shield the ladles or gating system with a controlled, inert atmosphere. Unfortunately, both of these possible approaches would present additional problems not existing presently. It would be very difficult and expensive to modify existing foundries to permit individual molds to be moved close to the furnaces or holding tanks. It also would be difficult and expensive to modify existing molten metal transfer equipment to provide a controlled, inert atmosphere all the way from the furnaces or holding tanks to the molds.